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CRJ down in Sweden

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CRJ down in Sweden

Old 11th Jan 2016, 18:01
  #61 (permalink)  
 
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possibly any water at the bottom of the crater mixed with residual jet fuel. Thus they had to pump out the mixture before working to retrieve important bits. Nothing significant about this
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Old 11th Jan 2016, 18:18
  #62 (permalink)  
 
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Can we assume that a problem with cargo e.g. Fire.....
Never "assume."

cf: https://en.wikipedia.org/wiki/Confirmation_bias
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Old 11th Jan 2016, 20:04
  #63 (permalink)  
 
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Although the flight surfaces on the CRJ are hydraulically actuated, there is no computer in between the pedals and the control column deciding weather the crew are flying safely or not and maybe just making matters worse such as on other FBW aircraft I know. So the flight surfaces should have done exactly as commanded.
Assuming that the linkage was not jammed by a foreign object such as a tool or frozen water/deicing fluid.
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Old 12th Jan 2016, 00:24
  #64 (permalink)  
 
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Originally Posted by Machinbird View Post
Assuming that the linkage was not jammed by a foreign object such as a tool or frozen water/deicing fluid.
Concur.

Or the AP was not engaged, as thats a 'computer' with a degree of authority over the flight controls. Or the stall protection COMPUTER didnt decide to do something. Or the Horizontal STabilizer Control Unit, likewise.

The number of aircraft where there isnt a computer of some kind involved nowadays is pretty small ....
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Old 12th Jan 2016, 03:56
  #65 (permalink)  
 
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Swedish AIBN wil have to wait for summer for any further recovery attempts.

NRK: Will have to wait until the ground thaws (Google translate)
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Old 12th Jan 2016, 04:48
  #66 (permalink)  
 
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It think the crash site is about at right distance for descent initiation.
Is it possible cargo shifted forward once aircraft pitched down?
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Old 12th Jan 2016, 07:24
  #67 (permalink)  
ika
 
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Originally Posted by _Phoenix View Post
It think the crash site is about at right distance for descent initiation.
Is it possible cargo shifted forward once aircraft pitched down?
I believe a CRJ 200 is highly sensitive to load distribution but I'm sceptical it could be loaded with a c of g so far forward that elevator control became impossible. Bear in mind that at forward C of G limit there is enough elevator authority to rotate or flare the aircraft at takeoff or landing speeds and in the cruise the elevator will have dramatically more authority (forces proportional to square of speed, subject to actuator/structural limits and altitude density effects). It was apparently carrying mail. Unless there was a cartoon lead ball, which didn't roll backwards under acceleration and pitch up on takeoff, it seems unlikely. But someone with a CRJ load schedule can probably determine a realistically bad load distribution and corresponding moment and comment...
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Old 12th Jan 2016, 10:03
  #68 (permalink)  
 
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in the cruise the elevator will have dramatically more authority (forces proportional to square of speed, subject to actuator/structural limits and altitude density effects)
In other words you mean less elevator authority ika? Low IAS at cruise level methinks.
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Old 12th Jan 2016, 15:13
  #69 (permalink)  
 
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If the V/S reports are close to accurate then it seems inconsistent with a prolonged stall condition similar to other recent mishaps. The V/S seems just a bit too high... if we have 9000fpm then thats around 79kts and assuming a 45 degree path vector with forward speed of 9000 as well that gives us an aircraft speed of 111 knots. Now the IAS at higher altitude may be in stall territory but as they got down to lower levels then there should have been enough speed to give enough control authority to correct without losing more than a few thousand feet or less.
That is until you start considering other factors such as spatial disorientation and other human factors that have led to loss of control in other accidents.

One other CRJ crash I'm thinking about is the one where a couple of pilots on repositioning flight decided to try their hand at being test pilots and flew themselves right off the backside of the power curve, stalled the wing, cooked the turbines, and were never able to restart, and then ran out of altitude to make a runway. Yet there are still more differences than similarities here as the final impact in this crash seems much different as well the crew seeming to have a more catastrophic problem since they didn't have time to get more than a single mayday off.

Considering the location, there is a lot riding on getting the recovered memory modules to reveal their secrets.
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Old 12th Jan 2016, 15:35
  #70 (permalink)  
 
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That hole is not a stalled aircraft hole.

That is a very high speed near vertical hole.
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Old 12th Jan 2016, 16:52
  #71 (permalink)  
 
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The contents of the mayday call they reportedly made should have given the investigation team some early clues.
AH reports today:

On Jan 12th 2016 the SHK told The Aviation Herald that the distress call just contained the repeated words "Mayday", there was no further information in the call.
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Old 12th Jan 2016, 17:21
  #72 (permalink)  
 
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Originally Posted by pattern_is_full View Post
AH reports today:
I sure hope they can get useable data from the recorders - if not it's going to really hard to determine much from what little is left of the aircraft
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Old 12th Jan 2016, 17:56
  #73 (permalink)  
ika
 
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Originally Posted by darkbarly View Post
In other words you mean less elevator authority ika? Low IAS at cruise level methinks.
What sorry dog said! Sorry for not being clearer; air may be thin and IAS not that high at 33,000 feet but pretty soon after you start diving earthwards IAS and control authority will go up. There's a general surmise (not conclusive) from the images and other data that it went in fast, nose-first, in one piece rather than a stall or in flight break-up. At some point, let's say 15,000 feet, assuming (for this only) pilots were not incapacitated or disoriented, heading nose down at a fair pace, if one had functioning controls one would expect to pull up as far as possible (and as necessary throttle back). I don't know about others but if controls worked but a forward c of g hindered pull up, faced with the grim choice of the certainty of what the looming ground means versus the possibility of overstressing the airframe I'd probably spend my last 60 seconds pulling hard back until either the nose stopped pointing at the ground or the elevator came off! Since they haven't located separate debris suggesting elevator detachment/damage it suggests to me that a c of g issue alone is unlikely. Some form of control issue, whether trim runaway, multiple hydraulic failure etc and/or a crew incapacitation issue must be considered, in my humble view. But feel free to disregard. I suspect most will agree, apart from the tragedy, is that it is both very curious and, unless the memory proves recoverable, unlikely we will know.
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Old 12th Jan 2016, 19:20
  #74 (permalink)  
 
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Since they haven't located separate debris suggesting elevator detachment/damage it suggests to me that a c of g issue alone is unlikely.
If part of the elevator (or tail) departed at high altitude, it could potentially be many miles from the (main) crash site. Given the remoteness of that whole area, such relatively small part(s) might not be located for months or even years.
I'd think that since they were able make a Mayday call, crew incapacitation would be unlikely, but as pattern_is_full noted, never 'assume' anything.
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Old 12th Jan 2016, 21:56
  #75 (permalink)  
 
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Having flown this type for many, many years, I can say a HS failure/runaway was probably my biggest concern.

This is a quality-made airframe and engine combination, but the electronics/trim switch/elevator feel system left a lot to be desired.
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Old 12th Jan 2016, 23:47
  #76 (permalink)  
 
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"The electronics/trim switch/elevator feel system left a lot to be desired."
Thanks, FIRESYSOK. Good to hear from someone with experience in the type.
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Old 13th Jan 2016, 08:05
  #77 (permalink)  
 
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There is also the Hoot Gibson maneuver that can be used to shave off unwanted speed. (Dropping the Gear)
@Machinbird

I'm glad you clarified ...

In my earlier days, the term was code for "erase the tapes"
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Old 13th Jan 2016, 14:47
  #78 (permalink)  
 
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Likely Stab Trim Runaway

Having flown both CRJ's and SE-DUX in its post cargo mod, I have to agree with the Stab Trim Runaway hypothesis. I haven't flown a 200 since 2011 but I know there was an SB or AW published after a couple of runaways in the U.S. a few years back. Whether DUX ever had it done will soon be revealed.
If I recall correctly the loads from OSL to TOS cubed out before they weighted out and were very well secured with a very simple system. In level flight or even in a normal 3 degree descent, the chance of trolleys coming loose was next to zero.
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Old 13th Jan 2016, 15:48
  #79 (permalink)  
 
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Re: post 78. Sometimes, someone posts something really good here. This is one of those times. Thank you.
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Old 13th Jan 2016, 16:26
  #80 (permalink)  
 
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There is no manual trim wheel on this type either.

It's happened to me that both pitch trim channels failed at cruise speed and we were left with an uncomfortably out-of-trim airplane as we slowed for approach.

I can only imagine if a HS runaway were not disconnected early via disconnect switches or CB, what the elevator forces would be with no manual trim reversion to correct the problem.
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